Treating cellulosic textiles



United States Patent 3,434,870 TREATING CELLULOSIC TEXTILES Henry Tovey, Silver Spring, Md., and Helmut F. Prahl,

Middleton, and Frederick M. Hart, Madison, Wis., assignors, by direct and mesne assignments, to Cotton Producers Institute, Memphis, Tenn., a non-profit corporation of Tennessee No Drawing. Filed Feb. 17, 1965, Ser. No. 433,456 Int. Cl. D06m 15/38 US. Cl. 117--106 15 Claims ABSTRACT OF THE DISCLOSURE Cellulosic material possessing improved shape holding properties as well as good abrasion resistance is obtained by first forming therein a graft polymer, such as by polymerization of a lower alkyl, hydroxyalkyl or aminoalkyl ester of acrylic or methacrylic acid, and thereafter treating the material with a thermosetting, creaseproofing resln.

This invention relates to a process for producing cellulosic fiber containing fabrics of improved properties. More particularly, it relates to a process for improving the abrasion resistance of resin treated cotton and cotton blend fabrics. Still more particularly, it relates to a process wherein an addition polymer is grafted onto the cotton fibers of a fabric prior to resin treatment.

It is well known to impart durable wrinkle resistance to cellulosic fabrics such as cotton by impregnation with an aqueous solution of a suitable thermosetting resinous precondensate or cellulose crosslinking agent, usually with an appropriate catalyst, and eventual curing of the impregnated fabric. Such treatments have been effective in improving the shape holding properties of cotton fabrics and have resulted in a greatly increased demand for wash-and-wear cotton fabrics because these combine the traditional comfort, washability and economy of the native fibers with the easy care properties desired in todays textile market. However, such resin treatment has also heretofore resulted in an adverse effect on some of the other important properties of cotton, notably its tensile strength and resistance to abrasion. Consequently, resin treated cotton fabrics have been known to be not quite as highly durable as plain finish cottons. Since the advent of the delayed-cure process for making shapeset garments, improvement in abrasion resistance of resin treated fabrics, especially at points of constant wear such as cuff edges, has become particularly desirable.

Considerable work has also been done in the past in various attempts to modify cellulosic fabrics by graft polymerizing ethylenically unsaturated monomers therein. In some instances laboratory tests have been reported indicating that such graft polymerization can result in some improvement in properties such as abrasion resistance and handle of otherwise untreated cotton fabrics, and also in some improvement in their wet crease recovery, especially when a hydrophobic graft polymer was applied at a low graft level. However, particularly as far as abrasion resistance is concerned, these indicated improvements have proved to be essentially illusory when tested under realistic conditions such as those to which garments are subjected in actual use, in laundering, etc. Moreover, such graft polymerization has been reported generally to result in an impairment of dry crease recovery, possibly because the graft polymer hinders hydrogen bonding within the cellulose, and thus makes it easier for the molecules to slip past each other under stress. As a result, the strain or deformation producted by a given stress increases, a larger proportion of the energy applied 3,434,870 Patented Mar. 25, 1969 is dissipated, and permanent set becomes greater. See H. Tovey, Textile Research Journal, March 1961, pp. 252, (particularly pp. 189-192).

It is an object of this invention to produce cellulosic fabrics having both good shape holding properties and good abrasion resistance. It is a more specific object of this invention to improve the abrasion resistance of resin treated cotton fabrics. Another object is to provide a process for producing cotton fabrics which retain a high degree of abrasion resistance after resin treatment, despite the known adverse effects of such treatment. A still more specific object is to provide a process for modifying cotton fabrics to provide an improved substrate which on subsequent resin treatment produces farbics possessing both excellent wrinkle resistance and excellent abrasion resistance.

It has now been discovered that despite the essentially indifferent and often adverse effects previously encountered in modifying cotton by polymer grafts, these various objects can be achieved by depositing or grafting certain kinds of addition polymers onto the cotton fabric in combination with conventional resin treatment. More particularly it has been surprisingly found that grafting of a relatively small amount of polymer onto a cellulosic fabric can be used as a means for improving its ultimate abrasion resistance without interfering with the effectiveness of thermosetting resin treatments, and that the resulting improvement in abrasion resistance is far greater than could be expected on the basis of any improvement obtained by the graft alone. Still more surprisngly, it has been found that such polymer grafting is most effective when it is applied prior to resin treatment, and is largely ineffective when applied after the resin treated fabric has been cured. Furthermore, while the invention can be carried out in a variety of ways, it has been found that particularly good results are obtained when the graft polymerization is carried out in vapor phase and that unusually uniform grafting over large areas of fabric can be achieved by first treating the fabric with a polymerization catalyst bath wherein a small amount of a surfactant has been included to insure good and uniform distribution of the catalyst on the fabric before it is brought into contact with the polymerizable monomer.

The nature, scope, and operation of the invention will become more fully apparent from the following description, it being understood, of course, that the invention is not intended to be limited to the particular embodiments described. Unless otherwise indicated, all amounts and proportions of materials are to be understood as being expressed on a weight basis throughout this: application and the appended claims.

The process of the present invention can be used on all types of cellulosic materials, including regenerated cellulose such as viscose, but is especially useful in treating natural cellulose materials such as cotton or linen or blends of such natural fibers with synthetics such as polyester, acrylic or nylon fibers. It can be applied to loose fibers, filaments, non-woven fabrics or bats and other material, to yarns, and to materials in an intermediate stage of conversion into yarn, such as condensed sliver, but it is most conveniently applied to woven, knitted or tufted fabrics. It can be applied to mercerized as well as unmercerized materials, either before or after dyeing, printing or other finishing treatments, to any form of such materials which are receptive to uniform wetting with the required aqueous treating solutions and to the formation of at least 2% of a graft polymer in the material. Sized material is preferably desized prior to use in the present process. The invention has been found particularly effective as applied to cotton fabrics of relatively lightweight, i.e., such as print cloth or shirting (fabrics weighing 3 to 5 ounces, or less, per square yard).

The principal agents used in this invention are, in the first step, a graft polymerizable monomer, an appropriate polymerization initiator or catalyst, and preferably also a surface active agent which can be included in the catalyst bath to obtain a particularly desirable end product. In the second essential step any of the thermosetting resins such as the various hardenable aminoplasts or the various curable glycidyl ethers or polyepoxides such as those described in U.S. Patent 3,026,216 to Sookne, or various other cellulose crosslinking agents known to improve the wrinkle resistance of cellulosic materials such as formaldehyde can be employed. Each of these is usually used in conjunction with an appropriate curing catalyst, all in a manner which is well known per se.

For instance, one may use a creaseproofing agent chosen from among polymethylol ureas, polymethylol melamines, methoxymethyl ureas and melamines, 1,3-dimethylol 4,S-dihydroxymonoureines, 1,3-dimethylol 5-N- alkyl triazones, dimethylol ethylene urea, dimethylol propylene urea, dimethylol carbamates, polymethylol hydrazinates, dimethylol bis amides, tetramethylol acetylene diureines, tris aziridinyl phosphine oxide, diglycidyl ethers of polyols, vinylcyclohexene dioxide, divinyl sulfone, bis hydroxyethyl sulfone, glycerine dichlorohydrin, epichlorohydrin, glyoxal, glutaraldehyde, acroleinformaldehyde resins, etc. Particularly convenient are the triazines obtained by condensing melamine and formaldehyde and the precondensates of urea, thiourea or cyclic ethylene urea with formaldehyde. Especially good results are obtained with dihydroxy dimethylol cyclic ethylene urea or imidazolidene resin of the type described in U.S. Patent 3,049,446 to Goldstein et al. and also with dimethylol melamine or trimethylol melamine precondensates, i.e., products obtained by condensing one mol of melamine with about two or preferably three mols of formaldehyde.

The graft polymerizable compound used in this invention may be a vinyl compound corres onding to the general formula wherein R may be hydrogen, a methyl group or chlorine and R may be a carboxyalkyl or substituted carboxyalkyl group containing from 1 to about 6 carbon atoms per alkyl radical. Thus, representative examples of such compounds include preferably the lower esters of acrylic and methacrylic acids such as methyl acrylate, n-butyl acrylate, 2-ethoxyethyl acrylate, diethylaminoethyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, dimethyl aminoethyl methacrylate, t-butyl aminoethyl methacrylate, etc. Still other vinyl compounds such as vinyl chloride and vinylidene chloride may also be used. The preferred compounds are those which have a relatively high vapor pressure at a temperature of about 100 C., e.g., those which boil at a temperature below about 175 C. at atmospheric pressure, so as to permit the grafting step to be carried out efficiently in the vapor phase at temperatures between about 25 C. and 100 C. The lower alkyl, alkoxyalkyl and aminoalkyl esters of acrylic and of methacrylic acid having such volatility characteristics are particularly preferred. Of course, optimum grafting procedures may vary somewhat from monomer to monomer as well as from fabric to fabric and it is therefore advisable to establish optimum conditions for each case by preliminary empirical tests.

Any conventional polymerization initiator system may be used in conjunction with such monomers. Aqueous solutions of an alkali metal or ammonium salt of persulfuric acid or of perboric acid are particularly preferred, but solutions of water-insoluble peroxygen compounds, e.g., benzoyl peroxide, cumene hydroperoxide, etc. in an appropriate organic solvent can also be used in a manner which is well known in the polymerization art. In addition to such oxygen yielding catalyst it is also desirable for the catalyst system to include in solution a small amount of a reducing compound such as a watersoluble salt of an oxyacid of sulphur, thereby forming a redox system of a type otherwise well known in the addition polymerization art. Such reducing compounds may accordingly include, for instance, sodium bisulfite or, more broadly, a hydrosulfite, sulfoxylate, pyrosulfite or thiosulfate of an alkali metal or of ammonium.

More specifically, the catalyst solution may contain from about 0.5 to 5% of the oxygen-yielding compound and about 0.2 to 4% of the reducing compound. Preferably the aqueous catalyst solution contains about 1.1 to 5 parts of the water-soluble oxygen-yielding compound per part of the reducing compound. In addition, the catalyst solution may optionally also include about 0.001 to 0.5% of a surfactant such as an alkyl ether of polyethylene glycol or an ethoxylated octyl or nonyl phenol, polyoxyethylene sorbitan monolaurate, polyoxyethylene stearate, polyoxyethylene lauryl alcohol, sodium heptadecyl sulfate, sodium di(2-ethylhexyl) phosphate, sodium tetradecyl sulfate, sodium Z-ethylhexyl sulfate, etc. When a surfactant is used, it may be virtually of any kind, ionic or non-ionic, the only requirement being that it not interfere with the polymerization reaction. Inclusion of the surfactant tends to give particularly uniform distribution of the graft in the fabric.

Graft polymerization of the monomer on the cellulose fibers may be effected in any known manner, including polymerization in liquid organic solution or in aqueous emulsion, using peroxidic or other free radical yielding catalysts such as bisazobutyronitrile, gamma-ray initiation, etc. However, it is particularly preferred to conduct the graft polymerization in vapor phase. In such a case the catalyst is applied to the cellulosic material before exposure to the monomer vapors, by soaking the material in a dilute solution of the catalyst. Excess solution is desirably removed from the material by squeezing, leaving, for instance, a wet pickup of between about 50% and 300%, e.g., between about and of an aqueous catalyst solution on the fabric before the polymerizable monomer is applied to it. Some moisture tends to facilitate the desired graft polymerization.

The grafting process can be conveniently carried out in an apparatus such as that shown in U.S. Patent 3,046,- 078, wherein the textile material is exposed to monomer vapors in a polymerization zone as the material is conveyed through it. Vaporization of the monomer is desirably promoted by bubbling carbon dioxide through a pool of liquid monomer which is maintained in the bottom portion of the polymerization chamber at a temperature of between about 40 and 80 C., e.g., between 50 and 70 C. It is particularly desirable to first saturate the carbon dioxide with water vapor by passing it through a gas bubbler filled with warm water. The textile material should remain exposed to the monomer atmosphere in the polymerization chamber long enough to allow the formation of between about 2% and 30% graft polymer therein. Residence times of between about 5 and 60 minutes, e.g., 15 to 45 minutes are usually adequate and can be readily obtained by proper adjustment of the rate of travel of the textile material through the polymerization chamber or, if desired, by maintaining the material stationary therein for the required time. When desired, the material may be passed through the polymerization chamber several times in sequence until the desired polymer add-on is achieved. A dry polymer add-on of from about 2 and up to about 30 percent or more, preferably from 4 to 20 percent, based on the weight of the fabric, is suitable.

The polymerization equipment is preferably lined with glass or made of aluminum. Many metals other than aluminum tend to react with the catalyst and especially when in contact with the textile material being treated, can cause uneven grafting.

Upon completion of the graft polymerization the material is desirably washed with an appropriate solvent to remove ungrafted homopolymer and then with water to remove residual catalyst. When using an acrylic acid ester as the monomer in the polymerization step the unwanted homopolymer can be readily removed from the material with a lower ketone solvent such as acetone or methyl ethyl ketone, or with lower alkyl ester of a saturated carboxylic acid such as ethyl acetate, etc.

The washed, grafted fabric is then ready to be made creaseproof or wrinkle resistant by an otherwise conventional treatment with one of the creaseproofing resins or agents described earlier herein.

When the precondensates are freely soluble in water they are used in the form of aqueous solutions, while those of limited water solubility are used either in the form of colloidal dispersions or in the form of solutions after the condensation products have been rendered soluble with the aid of acids.

The aqueous impregnation bath may contain about 3 to 20 weight percent of hardenable aminoplast or other creaseproofing agent, either in solution or in emulsion. Depending on the requirements of the finished fabrics, the impregnation is carried out in such a manner that the dry add-on of creaseproofing agent on the material is between about 1 and 20 percent, preferably between about 2 and percent, based on the weight of fibrous material. The optimum add-on is determined mainly by factors such as the type of creaseproofing agent and catalyst used, the effectiveness of the final curing technique employed, and the amount of strength loss one can afford. A relatively high add-on will impart a good resilience to the material even when a relatively mild curing technique is employed, but will also result in a greater strength loss than is caused by a lower add-on.

The catalyst is desirably present in a concentration within the range between about 0.5 and percent, preferably between 2 and 10 percent, by weight of the creaseproofing agent. The Optimum proportion depends on the specific types of chemicals employed as well as on the time and temperature of the curing procedure followed, and can be readily determined by preliminary empirical test. Curing catalysts commonly employed for the curing of thermosetting aminoplasts, diepoxides, or aldehydes commonly include acidic salts of suitable polyvalent metals such as magnesium chloride or nitrate, or zinc chloride or nitrate; various amine hydrochlorides such as 2-amino-2-methyl-l-propanol hydrochloride, or triethanolamine hydrochloride; and ammonium salts such as ammonium sulfate, chloride, nitrate, tartarate, citrate, formate, oxalate, or ammonium ethyl phosphate, or ammonium dihydrogen phosphate or the like. Organic acids, particularly those having a high melting point, e.g., above about 120 C. such as malonic, oxalic or succinic acid are similarly useful. For alkali catalyzed creaseproofing agents such as the sulfones and the chlorohydrins, the catalyst may be sodium carbonate, sodium hydroxide, etc. Other acidic or alkaline catalysts may also be used. The addition of a wetting agent, though not usually necessary, can be helpful when the condition of the fibrous material does not permit the impregnating bath to penetrate with the desired degree of readiness or evenness. When the curing catalyst is included in an aminoplast rather than being applied to the fabric from a separate bath, it is preferable to keep the pH of the bath on the alkaline side, e.g., between about 7.5 and 9 in order to guard against possible premature condensation. This precaution is particularly advisable if the catalyst containing resin bath is to be kept usable for an extended period.

The treatment with the creaseproofing agent and catalyst can be done by conventional padding using customary equipment, or by spraying, or by other known processes involving the application of the creaseproofing formulation to the fabric, squeezing off excess liquor, drying the fabric, and then curing it at an elevated temperature (e.g., 275 to 375 F.) to set the creaseproofing resin or to accomplish the desired crosslinking of the cellulose molecules, all of which has been practiced in the art for many years now. Alternatively, instead of curing the resin promptly after its application to the fabric, it is also possible to employ the more recently developed delayed cure technique of the type described, for instance, in US. Patent 2,974,432 to W. K. Warnock et a1. By this technique, the chemically impregnated fabrics are dried at a moderate, noncuring temperature but not immediately cured. Instead, the dried fabrics are first cut, made into garments, pressed into shape, and only then heated to an elevated temperature to cause the creaseproofing agent to cure.

Softeners or plasticizers such as silicone oils, polyethylene or oxidized polyethylene, or fatty based chemicals can also be included in the resin bath in a minor amount, e.g., 1 to 10% based on the creaseproofing agent, as is otherwise customary.

It should be understood, of course, that both the application of a creaseproofing resin to the fabric and its subsequent cure on the fabric are steps which are per se well known in the art. The novelty of this invention does not lie in any particular way of performing this known treatment but rather in the combination of this otherwise well known treatment with a polymer grafting step. It is this combination which has been discovered to produce fabrics possessing good creaseproofness combined with surprisingly good abrasion resistance, that is, a total improvement which is far greater than the sum of the effects Obtained when each of these treatments is performed without the other.

It may be significant that an equally favorable result as that obtained by graft polymerization. with subsequent resin treatment is not obtained when the sequence of steps is reversed, and the resin treatment precedes the graft polymerization step. While it is not intended that this invention be limited because of any theoretical explanations, it may be that by keeping the graft polymer add-on within moderate limits, as indicated above, the graft occupies principally the surfaces of the cotton fibers and the regions near the fiber surfaces, so that subsequent resin treatment cannot crosslink these portions of the fibers too extensively, but can penetrate into the more central portions of the fibers and thus perform its regular function. Thus, the combination of limited graft polymerization and resin treatment in accordance with this invention should produce a fiber structure having a highly flexible outer ring, or skin portion, and a highly crosslinked, resilient core portion. The resilient cores then can impart wrinkle resistance to the fibers without resulting in a great loss of abrasion resistance which otherwise occurs when conventional resin treatment extensively crosslinks the surface portions as well as the inner portions of fibers.

The following examples are illustrative of the process of the present invention and of the results obtained thereby but are not to be considered as limiting. On the contrary, persons skilled in the textile treating art should be able to develop other variations and modifications of this invention without departing from its spirit or from the scope of the appended claims. All quantities of materials are expressed herein on a weight basis unless indicated otherwise.

Example 1 A series of tests were performed to illustrate the effect of various treatments on the properties of X 80 bleached cotton print cloth. The tests involved a grafting step wherein n-butyl acrylate (nBA) was used as the polymerizable monomer.

The grafting procedure employed was as follows. First, an aqueous catalyst bath containing 2% ammonium persulfate and 1% sodium bisulfite was prepared by dissolving the persulfate (3.0 parts) and the bisulfite (1.5 parts) each separately in parts of distilled water,

and then combining the two solutions by pouring the bisulfite into the persulfate with rapid stirring.

After immersion in this catalyst bath for minutes at room temperature and squeezing out excess liquor, samples of the fabric containing about 120% wet pickup were suspended from aluminum hangers in the upper portion of a grafting chamber. On the floor of the grafting chamber was an open dish containing n-butyl acrylate monomer. The temperature in the chamber was held at 60 C., and carbon dioxide was bubbled as a carrier gas into the liquid monomer at atmospheric pressure. The carbon dioxide was first saturated with water vapor by passage through a gas bubbler filled with distilled water, also at 60 C. While CO was the most effective carrier gas in facilitating the desired polymer add-on other inert carrier gases such as nitrogen can be used similarly, or the use of any carrier gas can be omitted altogether when grafting rate is not particularly important. Polymerization inhibitors, such as mercaptans or thiazoles, should desirably be excluded from the polymerization zone, and for this reason the use of vulcanized rubber, for instance, in any part of the polymerization apparatus is best avoided.

Each graft polymerization was conducted for a period of 30 minutes whereupon the grafted samples were removed from the chamber, washed several times in acetone to remove homopolymer and once in distilled water to remove any excess catalyst. The whole catalyst impregnation and grafting process was repeated when it was desired to obtain a greater polymer add-on than could be obtained within one 30-minute period. Of course, continuous polymerization periods longer than 30 minutes may be used if a more persistent catalyst is used or if the active catalyst content of the fabric under treatment is from time to time otherwise appropriately replenished.

In tests involving resin treatment, the samples were conventionally treated with a mobile aqueous solution of a methylol imidazolidene resin. More specifically, a commercial aminoplast solution (Permafresh 183 brand, made by Sun Chemical Company) was used which contained 50% dihydroxy dimethylol cyclic ethylene urea in water. In making up the padding bath, 100 parts of this commercial solution were mixed with 18 parts of an aqueous solution containing 40% zinc nitrate, 11 parts of an aqueous dispersion of Mykon SF oxidized polyethylene to serve as a softener, and 425 parts of distilled water. The cloth samples were padded in this bath and then air-dried at ambient conditions. Final setting was effected by heating at an elevated temperature, e.g., by pressing with an electric iron set at cotton, followed by a 7-minute air-oven cure at 160 C.

The following five different groups of samples were prepared:

I. Blank (no graft, no resin).

II. Control (resin only).

III. Graft only.

IV. Grafted, then resin treated. V. Resin treated, then grafted.

Wrinkle recovery values were determined according to AATCC Method 66-1959 T using the Monsanto Wrinkle Tester. All samples that were resin treated had a Wrinkle recovery within the relatively narrow range of between about 140 and 155 degrees. In contrast, all the samples lacking resin treatment had substantially lower recovery values, regardless of whether or not they had polymer grafted on them. Graft treatment alone resulted in no improvement in wrinkle recovery as compared with the blank samples, even at polylmer add-ons of up to 30%. When the graft treatment was combined with a conventional resin treatment it did not impair the wrinkle recovery attributable to the resin treatment even at polymer odd-ons as high as 60%, but neither did it significantly improve the recovery produced by the resin treatment alone.

To determine the abrasion resistance of the several samples they were, rior to curing, cut to 6 x 6 inch size, then each was folded diagonally to form a triangle, cured, then sewn along the two open sides of the triangle and pressed. The test was performed by agitating the samples in a small (apartment-size) washing machine with a vertical center post, including with each load 305 one-inch squares of water proof sandpaper (No. 220 on one face and No. 400 on the other, glued back to back) to expedite abrasion. After 23 hours of continuous agitation in water the samples were dried for one hour in a rotating drum drier, just suflicient to reach dryness. The dried samples were then opened, photographed to make a permanent record of the extent of their abrasion and visually rated for abrasion. The data are summarized in Table I.

The data show that samples grafted and then resin treated in accordance with this invention (Group IV) resisted abrasion approximately as well as the untreated blanks (Group I), even at graft levels as low as 3 and 4%, but unlike the blanks they possessed good crease retention and wrinkle recovery. On the other hand, consistent with the generally known effect of resin treatment on the abrasion of cotton fabrics, the conventionally resin treated but ungrafted samples (Group II) as well as the samples which were first resin treated and only then grafted (Group V), while possessing good crease retention, showed much more Wear than the blanks.

TABLE I.AB RASION RESISTANCE Sample Graft, Resin, Crease Abrasion Percent Percent retention rating 1 Group I None None 1 I N one None 2 I I None 6. 7 3 II None 7. 6 5 II None 2 5. 4 4 III 4. 3 None 2 III 6. 8 None 1 III 27. 6 None 2 IV 7. 6 5. 5 2 IV 11. 0 5. 4 2 IV 4. 2 2 7. 7 2 IV 11.2 2 6. 2 2 V 3. 7 5. 1 4 V 4. 9 5. 4 3

51 Ilating: 1 no wear, 2 slight wear, 3 medium wear, 4 heavy wear,

R e s in cure delayed two days. Grafting alone (Group III) does not materially affect the abrasion resistance as compared with the blank but neither does it improve the crease retention or the wrinkle resistance of the fabric. Thus it can be seen that the grafting step on which the present invention is based is instrumental in producing cotton fabrics which are quite unusual in combining good Wrinkle resistance and crease retention with excellent abrasion resistance, but this result is obtained only when the grafting step is followed by a resin treatment.

Example 2 In another series of tests the following groups of samples were prepared from x 80 bleached cotton print cloth:

Group Sample Type I. Grafted, resin treated, immediate cure.

II. Grafted, resin treated, delayed (48 hours) cure. III. Resin treated only, immediate cure.

IV. Resin treated only, delayed (48 hours) cure.

V. No treatment (control).

VI. Grafted only.

VII. Grafted over resin treatment.

The same grafting and resin treating materials and procedures as well as the same test method and equipment were used as described in Example 1.

Tests showed that all of the resin treated samples had substantially equally good wrinkle resistance, both immediate and long term, regardless of whether or not the fabric had been grafted. However, a very pronounced difference in abrasion was noticed between sample groups I, II, V and VI on the One hand, which were only moderately worn, and sample groups III, IV and VII on the other hand, which were quite badly worn.

Groups I and II were then again returned t the abrasion test with the objective of abrading them further until the same degree of wear as groups III and IV was reached. At an additional 169 hours of washing and 3 hours of drying (total exposure, 384 hours of washing, 8 /2 hours of drying) these samples gave a visual appearance which approached, but was not quite as worn as, that of groups III and IV. Thus, under the indicated test conditions the grafted and resin treated cotton samples wore at least about 80% longer than equivalent resin treated samples which had not been grafted.

Examples 310 The general sample preparation procedure of Example 1 was repeated in another series of tests using in the grafting step one of the monomers shown in Table II below, this step being followed by the conventional resin treatment as previously described.

In each case a polymer add-on of between about 3% and on dry fabric weight was obtained in the grafting step, whereupon the resin treatment was applied as in Example 1. conventionally resin treated samples (controls) were also tested for comparison. In each case the polymer graft when followed by resin treatment gave a cotton fabric possessing good wrinkle resistance and TABLE II.ABRASION OF GRAFTED AND RESIN TREATED COTTON Abrasion rating Example (hours in Improve- No. Monomer washer to ment standard percent 1 abrasion) Control... None (resin only) 3. nButyl acrylate 19 27 4. 2-1nethoxyethyl acrylate 19 27 5. -ethoxyethyl acrylate-. 33 6. Methyl acrylate 30 100 7. Ethyl acrylate 31 107 8 Z-diethylaminoethyl acrylate-... 42 180 9 Z-dimethylaminoethyl 21 methacrylate. 10 2-t-butylamlnoethy1 29 93 methacrylate.

1 Average of at least three separate sample preparations and tests.

The tabulated data show that grafting with the various monomers prior to the resin treatment can easily improve the abrasion resistance of the final fabric by at least 25% as compared with the abrasion resistance of the conventionally resin treated control. In Examples 6, 7 and 10 the abrasion resistance of the control was doubled, and in Example 8 it was almost tripled. The C to C alkyl esters and the monoand dialkyl (C to C aminoethyl esters of acrylic or methacrylic acid have thus shown themselves to be especially effective. More broadly, the preferred class of grafting monomers can be said to correspond to the formula CH :CR-COOR wherein R is selected from the group consisting of hydrogen and methyl and R' is selected from the group consisting of alkyl groups having a total of 1 to 4 carbon atoms, alkoxyethyl groups having a total of 3 to 4 carbon atoms and monoand dialkyl substituted aminoethyl groups having a total of 3 to 6 carbon atoms.

Parenthetically it should be noted that this method of measuring and comparing abrasion resistance of fabrics inherently favors the untreated fabrics over those which have been resin treated. The reason for this is that the resin treated samples, which are creased by pressing and subsequent curing, retain a sharp edge during the washing operation, and abrasion is consequently concentrated on this edge. By contrast, the washing of samples which have not been resin treated causes them to rapidly lose any crease they may have been previously given, and hence abrasion such untreated fabrics undergo in the wash is spread over a wider area of the fabric and is therefore less severe than the abrasion undergone by the resin treated samples.

Example 11 This example illustrates the possibility of using an aque ous emulsion technique for applying a graft polymer to cotton in combination with a resin treatment.

In operating pursuant to this technique, an aqueous mixture is first prepared by mixing 150 parts of a 2% ammonium persulfate solution and 150 parts of a 1% sodium bisulfite solution and 2 parts of an alkyl ether of polyethylene glycol as a surfactant. 50 parts of methyl methacrylate is then added to this mixture. The methacrylate is emulsified in the aqueous mixture by high-speed agitation in a Waring blender.

5" X 5" squares of X 80 bleached cotton print cloth are immersed in the aqueous emulsion for 30 minutes at 25 C., in which time a substantial amount of polymer is formed. Thereafter the cloth samples are removed from the emulsion, washed twice with acetone and once with water, and then given a final acetone rinse prior to drying and weighing. About 10% polymer is thus permanently affixed to the cotton.

The resulting polymer containing cotton samples are then resin treated as described in Example 1 and tested for abrasion resistance by the wet abrasion test. In comparison with cotton samples which were resin treated without any prior polymerization step the samples treated in accordance with the present invention show a substantial improvement in abrasion resistance.

Example 12 In this example the graft polymerization step is carried out in liquid phase using still another technique. More specifically, 0.1 part of azobisisobutyronitrile is dissolved in parts of ethyl acrylate and the samples of the 80 x 80 bleached cotton print cloth are impregnated in the resulting solution. After squeezing out excess liquid the cotton samples are placed for 1 hour in an air oven maintained at 60 C., whereupon the samples are washed with acetone and with water as described in Example 11, dried and weighed. A polymer add-on of about 7% is achieved.

Finally, the samples are resin treated as before and their abrasion resistance determined in comparison with control samples which were resin treated in the conventional way, without application of any graft polymer to the cotton. Once more, a significant improvement in abrasion resistance of the samples treated in accordance with this invention is detected.

Now that the invention has been generally described and specifically illustrated in the foregoing disclosure, its

scope is particularly pointed out in the appended claims.

What is claimed is: 1. A process for forming textile material which contains cellulosic fibers possessing good crease resistance and good abrasion resistance, which process comprises:

(1) applying a polymerizable monomeric reactant con-.

sisting essentially of a lower ester of acrylic or methacrylic acid to a cellulosic textile material,

(2) maintaining a quantity of the monomeric reactant in contact with the cellulosic material under polymerization conditions until between about 2% and 30% of the monomeric reactant (based on the cellulosic material) is fixed in the form of a polymer in the cellulosic material, and

(3) thereafter treating the polymer-containing cellulosic material with a creaseproofing agent.

2. A process for imparting good crease resistance and good abrasion resistance to a cotton cellulose fabric, which comprises uniformly impregnating said fabric with an aqueous solution of water soluble peroxygen com pound to serve as a polymerization catalyst, vaporizing a monomer reactant consisting essentially of an acrylic compound corresponding to the formula CH zCR-COOR' wherein R is selected from the group consisting of hydrogen and methyl and R is selected from the group consisting of alkyl groups having a total of l to 4 carbon atoms, alkoxyethyl groups having a total of 3 to 4 carbon atoms and monoand dialkyl substituted aminoethyl groups having a total of 3 to 6 carbon atoms, contacting the catalyst-containing fabric with the resulting acrylic monomer vapors at a temperature between about 100 and 200 F. until between about 2% and 30% of acrylic polymer is grafted onto the cellulose and some acetonesoluble polymer is formed on the fabric, removing the actone-soluble polymer from the fabric, depositing on the fabric a creaseproofing amount in the range of about 1% to 20% of a hardenable aminoplast, and heating the fabric at a temperature between about 275 and 375 F. to cure the deposited aminoplast.

3. A process according to claim 2 wherein the fabric is a cotton cloth having a weight of between about 3 and 5 ounces per square yard.

4. A process according to claim 3 wherein the aminoplast is a heat curable resin of the methylol urea class.

5. A process according to claim 3 wherein the aminoplast is a dihydroxy dimethylol cyclic ethylene urea.

6. A process for imparting good crease resistance and good abrasion resistance to a cellulosic textile, which process comprises applying to the material in a POIYIDBII- zation step a vapor consisting essentially of a readily polymerizable monomer selected from the group consisting of lower alkyl, alkoxyethyl and aminoalkyl esters of acrylic acid and lower alkyl, alkoxyethyl and aminoalkyl esters of methacrylic acid in the presence of a free radical yielding polymerization catalyst under polymerization conditions until an acetone-insoluble acrylic polymer is grafted onto the cellulose and some acetone-soluble homopolymer is formed on the material in an amount of between about 4 and 20% based on the material, thereafter depositing a creaseproofing amount of a curable thermosetting resin on the polymer-containing material in a resin treating step, and eventually heating the resin treated material to set the resin and impart crease resistance to the material.

7. A process according to claim 6 wherein the catalyst is a peroxygen compound.

8. A process according to claim 6 wherein the monomer is an alkyl acrylate containing an alkyl group of between 1 and 4 carbon atoms.

9. A process according to claim 6 wherein the monomer is tertiary butyl acrylate.

10. A process according to claim 6 wherein the monomer is ethyl acrylate.

11. A process according to claim 6 wherein the fabric is a cotton cloth having a weight of between 3 and 5 ounces per square yard, the monomer is 2-diethylaminoethyl acrylate and the thermosetting resin as an aminoplast.

12. A process according to claim 6 wherein the cellulosic material is impregnated with an aqueous catalyst solution containing an inorganic peroxygen salt and thereafter exposed to vapors of the monomer.

13. A process according to claim 6 wherein acetonesoluble homopolymer is washed from the material after the polymerization step and in advance of the resin treat- 5 ing step.

14. A process according to claim 6 wherein after the polymerization step and in advance of the resin treating step acetone-soluble homopolymer is washed from the material with a liquid solvent selected from the group consisting of lower ketones and lower alkyl esters of saturated carboxylic acids, and residual polymerization catalyst is washed from the material with water.

15. A process according to claim 12 wherein the aqueous catalyst solution contains a surfactant in minor proportion sufficient to promote uniform distribution of the catalyst in the textile material.

References Cited UNITED STATES PATENTS 3,125,405 3/1964 Gardon 117-139.4 X 3,246,946 4/1966 Gardon 1l7-139.4 X 2,299,786 10/1942 Battye et al. 1l7139.4 2,406,453 8/1946 Charlton et al 117-47 2,406,454 8/1946 Charlton et a1.

3,026,216 3/1962 Sookne et al. 117139.4 3,049,446 8/1962 Goldstein et a1 117-143 WILLIAM D. MARTIN, Primary Examiner.

THEODORE G. DAVIS, Assistant Examiner.

US. Cl. X.R.

81l6, 116.2; 1l7-l39.4, 143, 145, 47, 56 

